PDCD1 and cancer: T cell-inflamed tumours show favourable survival outcomes in many cancer types,26–28 and a previous study showed a higher CD8+ T cell density in HPV-positive HNSCC tumours than in HPV-negative tumours.12 Moreover, evasion of the immune response against foreign HPV viral antigens in tumour cells is dependent on the PD-1/PD-L1 axis, suggesting that HPV-positive tumours are susceptible to the immune checkpoint pathway.29 Accordingly, the high T cell gene signature with positive HPV status of IR type tumours may explain the favourable prognosis and high responsiveness to anti-PD-1/PD-L1 therapy.